SYNTACTIC FOAM, PROCESS OF ITS PREPARATION AND BUOYANCY MATERIAL INCLUDING THE SAME

Abstract

Some embodiments are directed to a process for making a syntactic foam. Some other embodiments are directed to a process for manufacturing a buoyancy material including an outer shell and a syntactic foam. Still other embodiments are directed to the syntactic foam (or buoyancy foam) obtainable by this process. Some other embodiments are directed to a process of undersea extraction of oil including: using the syntactic. Still other embodiments are directed to an undersea extracting pipeline including a pipeline, and either the syntactic foam or the buoyancy material.

Claims

1. A process for making a syntactic foam comprising: a) mixing together a determined amount of a curable liquid resin monomer or prepolymer and a polymerization initiator in order to obtain an operable curable liquid resin; b) mixing at a determined temperature range the operable curable liquid resin with a determined amount of at least one type of low density micro-elements, said micro-elements being comprised in a sphere having a diameter comprised from 1 μm to 1 mm and being introduced continuously in the operable curable liquid resin and at a constant volumetric and/or mass flow rate, while limiting breakage of micro-elements; c) homogenizing at a determined temperature range and degassing the mixture of operable curable liquid resin and micro-elements in order to obtain an intermediate syntactic foam; d) casting at a determined temperature range the intermediate syntactic foam in a container optionally comprising a determined amount of macro-elements being comprised in a sphere of a diameter comprised from 1 mm to 10 cm; and e) hardening the operable curable liquid resin; wherein the temperature is regulated, in one or more of step(s) a) to e), to control and limit exothermic peak during step e), thereby obtaining the syntactic foam within the container.

2. The process according to claim 1, which is a continuous flow process.

3. The process according to claim 1, wherein the mixing of step a) is carried out by a mean of incorporating a solid phase into a liquid phase.

4. The process according to claim 3, wherein said mean is selected from the group comprising an endless screw, and a dispersing machine.

5. The process according to claim 1, in which said curable liquid resin is selected in the group comprising an epoxy resin, an epoxy bisphenol A diglycidyl ether based resin and a polyurethane resin.

6. The process according to claim 1, wherein the polymerization initiator is selected in the group comprising polyfunctional amines, acids, phenols, alcohols, thiols, polyols.

7. The process according to claim 1, wherein in step a), the ratio of epoxy resin monomer to polymerization initiator is comprised from 1 to 10.

8. The process according to claim 1, wherein the mixing of step b) is carried out by a mean selected from the group comprising an endless screw and a dispersing machine.

9. The process according to claim 1, wherein the mean temperature of step a) is of from 15 to 80° C.

10. The process according to claim 1, wherein the amount of microspheres in step b) is comprised from 10% to 65% in volume ratio in the syntactic foam.

11. The process according to claim 1, wherein the micro-elements are selected from the group comprising glass, ceramic, polymer, metal and carbon.

12. The process according to claim 1, wherein the constant volumetric and/or massic flow rate of step b) is comprised of from 5 to 30 kg/min and/or from 30 to 60 Kg/min.

13. The process according to claim 1, wherein the mixing of step c) is carried out by a mean selected from the group comprising an endless screw and a powder disperser.

14. The process according to claim 1, wherein the temperature of step c) is comprised from 10 to 80° C.

15. The process according to claim 1, wherein the determined mechanical force of step c) is selected from a shear force and an homogenization force resulting in less than 15% of breakage of the micro-elements.

16. The process according to claim 1, wherein the determined vacuum of step c) has a value less than the atmospheric pressure.

17. The process according to claim 1, wherein the macro-elements are macro-spheres and the micro-elements are micro-spheres.

18. The process according to claim 1, wherein the macro-elements are made in a material selected from a thermosetting resin such as an epoxy resin or a polyester resin, a thermoplastic resin such as polyethylene, ceramic and steel.

19. The process according to claim 1, wherein the temperature of step d) is maintained at a temperature that causes no damage to the syntactic foam.

20. The process according to claim 1, wherein the volume of syntactic foam casted into the container is greater than 1 liter.

21. The process according to claim 1, wherein the casting of step d) is realized in several successive castings.

22. The process according to claim 1, wherein step e) of hardening the operable curable liquid resin is realized at a temperature that causes no damage to the macro-elements.

23. The process according to claim 1, wherein the steps a) to e) are carried out in a batch or a continuous flow process.

24. The process according to claim 1, wherein the obtained syntactic foam has a density of from 200 kg/m.sup.3 to 800 kg/m.sup.3.

25. The process according to claim 1, wherein the buoyancy of the syntactic foam is defined according the principle (I):
Buoyancy=V.sub.Shell×(ρ.sub.fluid−ρ.sub.COMPOSITE SYNTACTIC FOAM) (I) wherein:
ρ.sub.COMPOSITE SYNTACTIC FOAM=%.sub.Volume Macrosphere×ρ.sub.Macrosphere+%.sub.Volume Experimental syntactic foam×ρ.sub.Experimental syntactic foam
ρ.sub.Experimental syntactic foam=γ.sub.Process×(%.sub.Volume Hardener×ρ.sub.Hardener+%.sub.Volume μsphere×ρ.sub.μsphere%.sub.Volume Resin×ρ.sub.Epoxy) γ.sub.process is the factor taking into account: process loss, remaining void in the matrix, shrinkage during polymerization, microsphere breakage ratio. ••%.sub.Volume Macrosphere Calulation: $%_{Volume .Math. .Math. Macrosphere} = 1 - %_{porosity} = \frac{V_{wall .Math. .Math. affected}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. affected .Math. .Math. by .Math. .Math. the .Math. .Math. wall}) + \frac{V_{closed .Math. .Math. packed}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. close .Math. .Math. packed})$ V.sub.wall affected is the volume occupied by all halves marcospheres in contact with the shell.
V.sub.closed packed=V.sub.shell−V.sub.wall affected

26. The process according to claim 1, wherein the volume percent of macro-element is from 10 to 99% in the resin.

27. A process for manufacturing a buoyancy material comprising an outer shell and a syntactic foam, the manufacturing process comprising: a) mixing together a determined amount of a curable liquid resin monomer or prepolymer and a polymerization initiator in order to obtain an operable curable liquid resin; b) mixing at a determined temperature range the operable curable liquid resin with a determined amount of at least one type of low density micro-elements, said micro-elements being comprised in a sphere having a diameter comprised from 1 μm to 1 mm and being introduced continuously in the operable curable liquid resin and at a constant volumetric and/or mass flow rate, while limiting breakage of micro-elements; c) homogenizing at a determined temperature range and degasing the mixture of operable curable liquid resin and micro-elements in order to obtain an intermediate syntactic foam; d) casting at a determined temperature range the intermediate syntactic foam in a container optionally comprising a determined amount of macro-elements being comprised in a sphere of a diameter comprised from 1 mm to 10 cm; and e) hardening the operable curable liquid resin; wherein the temperature is regulated, in one or more of step(s) a) to e), to control and limit exothermic peak during step e), wherein the container determines the outer shell of the buoyancy, thereby obtaining the buoyancy material.

28. The process according to claim 27, which is a continuous flow process.

29. The process according to claim 27, wherein the mixing of step a) is carried out by a mean of incorporating a solid phase into a liquid phase.

30. The process according to claim 29, wherein said mean is selected from the group comprising an endless screw, and a dispersing machine.

31. The process according to claim 27, in which said curable liquid resin is selected in the group comprising an epoxy resin, an epoxy bisphenol A diglycidyl ether based resin and a polyurethane resin.

32. The process according to claim 27, wherein the polymerization initiator is selected in the group comprising polyfunctional amines, acids, acid anhydrides, phenols, alcohols, thiols.

33. The process according to claim 27, wherein in step a), the ratio of epoxy resin monomer to polymerization initiator is comprised from 1 to 10.

34. The process according to claim 27, wherein the mixing of step b) is carried out by a mean selected from the group comprising an endless screw and a dispersing machine.

35. The process according to claim 27, wherein the mean temperature of step a) is of from 5 to 80° C.

36. The process according to claim 27, wherein the amount of microspheres in step b) is comprised from 10% to 73% in volume ratio in the syntactic foam.

37. The process according to claim 27, wherein the micro-elements are selected from the group comprising glass, ceramic, polymer, metal and carbon.

38. The process according to claim 27, wherein the constant volumetric and/or mass flow rate of step b) is comprised of from 5 to 30 kg/min and/or from 30 to 60 Kg/min.

39. The process according to claim 27, wherein the mixing of step c) is carried out by a mean selected from the group comprising an endless screw and a powder disperser.

40. The process according to claim 27, wherein the temperature of step c) is comprised from 10 to 80° C.

41. The process according to claim 27, wherein the determined mechanical force of step c) is selected from a shear force and an homogenization force resulting in less than 20% of breakage of the micro-elements.

42. The process according to claim 27, wherein the determined vacuum of step c) has a value less than the atmospheric pressure.

43. The process according to claim 27, wherein the macro-elements are macro-spheres and the micro-elements are micro-spheres.

44. The process according to claim 27, wherein the macro-elements are made in a material selected from a thermosetting resin such as an epoxy resin or a polyester resin, a thermoplastic resin such as polyethylene, ceramic and steel.

45. The process according to claim 27, wherein the temperature of step d) is maintained at a temperature that causes no damage to the syntactic foam.

46. The process according to claim 27, wherein the volume of syntactic foam casted into the container is greater than 1 liter.

47. The process according to claim 27, wherein the casting of step d) is realized in several successive castings.

48. The process according to claim 27, wherein step e) of hardening the operable curable liquid resin is realized at a temperature that causes no damage to the macro-elements.

49. The process according to claim 27, wherein the steps a) to e) are carried out in a batch or a continuous flow process.

50. The process according to claim 27, wherein the obtained syntactic foam has a density of from 200 kg/m.sup.3 to 800 kg/m.sup.3.

51. The process according to claim 27, wherein the buoyancy of the syntactic foam is defined according the principle (I): $\begin{matrix} .Math. Buoyancy = V_{Shell} \times (ρ_{fluid} - ρ_{COMPOSITE .Math. .Math. SYNTACTIC .Math. .Math. FOAM}) .Math. .Math. .Math. wherein .Math. : .Math. .Math. ρ_{COMPOSITE .Math. .Math. SYNTACTIC .Math. .Math. FOAM} = %_{Volume .Math. .Math. Macrosphere} \times ρ_{Macrosphere} + %_{Volume .Math. .Math. Experimental .Math. .Math. syntactic .Math. .Math. foam} \times ρ_{Experimental .Math. .Math. syntactic .Math. .Math. foam} .Math. .Math. ρ_{Experimental .Math. .Math. syntactic .Math. .Math. foam} = γ_{Process} \times (%_{Volume .Math. .Math. Hardener} \times ρ_{Hardener} + %_{Volume .Math. .Math. μ .Math. .Math. sphere} \times ρ_{μ .Math. .Math. sphere} + %_{Volume .Math. .Math. Resin} \times ρ_{Epoxy}) & (I) \end{matrix}$ ρ.sub.process is the factor taking into account process loss, remaining void in the matrix, shrinkage during polymerization and microsphere breakage ratio $%_{Volume .Math. .Math. Macrosphere} .Math. .Math. Calculation .Math. : .Math. .Math. %_{Volume .Math. .Math. Macrosphere} = 1 - %_{porosity} .Math. .Math. %_{Volume .Math. .Math. Msphere} = \frac{V_{wall .Math. .Math. affected}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. affected .Math. .Math. by .Math. .Math. the .Math. .Math. wall}) + \frac{V_{closed .Math. .Math. packed}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. close .Math. .Math. packed})$ V.sub.wall affected is the volume occupied by all halves marcospheres in contact with the shell.
V.sub.closed packed=V.sub.shell−V.sub.wall affected

52. The process according to claim 50, wherein % Volume macro-element is from 50 to 99% in the resin.

53. The process according to claim 52, wherein the buoyancy material is manufactured to float at a distance from the surface of the sea of 200 m.

54. The process according to claim 52, wherein the buoyancy material is manufactured to float at a distance from the surface of the sea of 600 m.

55. The process according to claim 52, wherein the buoyancy material is manufactured to float at a distance from the surface of the sea of 4000 m.

56. The syntactic foam obtainable by the process accordingly to claim 1, including macro-elements dispersed in a mixture of a matrix comprising a curable liquid resin and low density microelements, in which said macro-elements are comprised in a sphere of a diameter comprised from 1 mm to 10 cm and said micro-elements being comprised in a sphere having a diameter comprised from 1 μm to 1 mm.

57. A buoyancy material comprising: a syntactic foam obtainable by the process according to claim 1.

58. A buoyancy material obtainable by carrying out the process according to claim 27.

59. A process of undersea extraction of oil, comprising: using a syntactic foam according to claim 1.

60. The process according to claim 59, wherein the syntactic or buoyancy material handles at a defined undersea level undersea extracting a pipeline.

61. An undersea extracting pipeline comprising: a pipeline, and a syntactic foam as defined in claim 56.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0103] FIG. 1 shows demonstration of a Distributed Buoyancy Module used in order to lighten a flexible pipe, the diameter of which is 338 mm, including a water injection riser, and having a shell (container) thickness of 10 mm, and a syntactic foam volume in the half shell of 1.56 m.sup.3.

[0104] FIG. 2 shows demonstration of a Modular Installation Buoyancy in order to lighten an equipment during installation steps.

[0105] FIG. 3 shows Buoyancy Principle, with Buoyancy, m.sub.object, ρ.sub.fluid and ρ.sub.object.

[0106] FIG. 4 shows the syntactic foam with water absorption (arrows), with Polymer Matrix (1) and Micro Glass Bubbles and/or Macro Spheres (2).

[0107] FIG. 5 shows with a (A): Buoyancy module internal view; A Buoyancy Module has been cut in order to control the core of the syntactic foam of the invention; a Buoyancy Module Shell (3) consisting of 8 mm low Linear Density Polyethylene and a Composite Syntactic Foam of the invention (4). (B-Scale: 1 cm=2.5 cm): Syntactic Foam of the invention composed for example by Epoxy Matrix and Hollow Glass Microspheres (5) and Hollow Polymer Macro Sphere (6). (C): Hollow Glass Microspheres in the matrix.

[0108] FIG. 6 shows Glass micro-spheres before blended in the matrix.

[0109] FIG. 7 shows Glass micro-spheres microscope view.

[0110] FIG. 8 shows Thermoplastic Macrosphere.

[0111] FIG. 9 shows Buoyancy measurement procedure.

[0112] FIG. 10 shows the three steps for the determination of buoyancy, as a function of net buoyancy during the design period between the buoyancy at service pressure and the buoyancy at the end of service life, with the buoyancy targeted after manufacturing, the net buoyancy at start of design period, and the net buoyancy at end of service life.

[0113] FIG. 11 shows the effect of the shell wall on the porosity between spheres. (A): effect of the wall on packing. (B): porosity in function of the distance to the wall expressed in sphere diameter.

[0114] FIG. 12 shows (A) an Example of the effect of the shell wall on the porosity with a cube, detail Closed Packed Volume/Volume Affected by the wall of the shell. (7) is the volume Total of the Shell (in grey): V.sub.shell. (8) is the distance between the wall of the shell and the volume closed packed 0.5×Macrosphere Diameter. (9) is the volume inside the shell affected by the wall: V.sub.wall affected. (10) is the volume closed packed (in red): V.sub.closed packed. (B) shows a buoyancy module shape, having an external diameter (a), an internal diameter (b) and a height (c).

[0115] FIG. 13 shows the syntactic foam casting machine principle, containing: an output (11), a Head Mixing and a Unit Mix Microsphere with Matrix (12), a vacuum unit that removes Air bubble in the Mix (13), a Pre-Mix binder and a Mix 2 Epoxy components (14), Fillers Hopper Receiving fillers from the top (15), a Microsphere Metering Hopper (16), a Hardener Intermediate Tank regulate in temperature (17), a Mass Flow Meter Regulate in line the mass flow of each matrix component temperature (18), a resin intermediate tank regulate in temperature (19).

[0116] FIG. 14 shows the process for buoyancy module product (part 1 to 6).

EXAMPLES

Example 1: Material Description

[0117] 1.1 Product Example: Distributed Buoyancy Module

[0118] The syntactic foam of the invention is casted inside a shell or a mold, the volume casted may be contained between 30 liters to 3-4 m.sup.3 per parts.

[0119] Distributed buoyancy modules generally consist of an internal clamping system and syntactic foam buoyancy elements. The buoyancy elements may be supplied in two halves incorporating a molded internal recess that is configured to transfer the forces from the buoyancy to the clamp and subsequently the riser.

[0120] This recess also accommodates bending of the riser during service. The internal clamping system may be fixed to the pipe and the two half modules may be fastened around the clamp. See FIG. 1.

[0121] 1.2 Product Example: Installation Modular Buoyancy

[0122] The installation modular buoyancy mostly used during installation phases. With this kind of buoyancy, the goal is to reduce handling needs and facilitate the installation of heavy material.

[0123] In the water, equipment with high weight coupled to modular buoyancy, the apparent weight of the 2 equipment can be null.

[0124] See FIG. 2.

[0125] 1.3 Physical Principle

[0126] The Syntactic foam shall provide buoyancy, at determined depth under water, without loose performance over years. These 3 physicals principles are explained in the next 3 chapters.

[0127] 1.3.1 Buoyancy

[0128] Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. [0129] Archimedes of Syracuse. See FIG. 3, providing the buoyancy principle, in which:

[0130] Buoyancy=Vertical ascending Force pushing the submerged object to the surface

m.sub.object=In this case the mass of the syntactic foam in air
ρ.sub.fluid=In this case ρ.sub.sea water
ρ.sub.object=In this case ρ.sub.syntactic foam
In our case object is wholly immersed in the fluid:

V.sub.sea water displaced=V.sub.syntactic foam=V

Buoyancy=m.sub.syntactic foam−m.sub.sea water displaced

Buoyancy=V×ρ.sub.syntactic foam−V×ρ.sub.sea water

Buoyancy=V×(ρ.sub.syntactic foam−ρ.sub.sea water)

[0131] Where:

[0132] m in kg

[0133] V in m.sup.3

[0134] ρ in Kg/m.sup.3

[0135] Buoyancy in kg

[0136] 1.3.2 Hydrostatic Pressure

[0137] The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above.

[0138] Hydrostatic pressure in a liquid can determined using the following equation:

p.sub.hydro=h×p×g

[0139] where

[0140] p=pressure (N/m.sup.2, Pa)

[0141] h=height of fluid column, or depth in the fluid at which the pressure is measured (m)

[0142] ρ=density of liquid (kg/m.sup.3)

[0143] g=the gravitational constant (9.81 m/s.sup.2)

[0144] Simplifying, a quick way to determine the hydrostatic pressure function the depth in the seawater is to approximate that each 10 m deeper in sea water the pressure increase 1 bar.

[0145] 100 SWM.fwdarw.10 bars

[0146] 1000 SWM.fwdarw.100 Bars

[0147] 1.3.3 Water Absorption

The water absorption is the capacity of the material to absorb water in wet condition. In the case of Syntactic Foam in subsea condition, the water absorption can be limited (less than 5% on 25 years) and controlled.

[0148] The syntactic foam is particularly adapted for this condition. All void created in the foam is encapsulated in a closed cell sphere. These spheres are infused in a polymer matrix.

[0149] All material used are specifically developed in order to have a very stable behaviour over the service life. See FIG. 4.

[0150] The use of micro-elements as Micro Glass Bubbles and macro-elements as macro sphere in a curable liquid resin as Epoxy Matrix does not allow the water to ingress inside the foam and ensures the foam performance during the service life.

[0151] 1.4 Principle of the Syntactic Foam of the Invention

[0152] The syntactic foam of the invention is a Composite Syntactic Foam.

[0153] Generally speaking, a syntactic foam is a composite closed cell foam. Cells are created by blending micro hollow spheres inside a polymer matrix.

[0154] In the syntactic foam of the invention are added macro elements, for example hollow marco-elements, in order to reduce the density.

[0155] See FIG. 5.

Example 2: Composition of the Composite Syntactic Foam of the Invention

[0156] 1. Micro-Elements

[0157] Micro-elements may be selected from the group including: glass, ceramic, polymer, metal and carbon.

[0158] In one embodiment, micro-elements are hollow glass microspheres.

[0159] Glass Bubbles are engineered hollow glass microspheres that are low-density particles.

[0160] There are used in the matrix to: [0161] Reduce foam density.fwdarw.Range density start from 125 kg/m.sup.3 to 600 kg/m.sup.3 [0162] lower costs [0163] enhance product properties

[0164] The spherical shape of glass bubbles offers a number of important benefits, including: [0165] higher filler loading [0166] reduced shrinkage and warpage [0167] high hydrostatic pressure strength.

[0168] The chemically stable soda-lime-borosilicate glass composition of glass bubbles provides excellent water resistance. They are also non-combustible and non-porous, so they do not absorb resin. And, their low alkalinity gives glass bubbles compatibility with most resins, stable viscosity and long shelf life.

[0169] See FIGS. 6 and 7.

[0170] 2. Macrospheres

[0171] Macro-elements may be in a material selected from the group including a thermosetting resin such as an epoxy resin or a polyester resin, or a thermoplastic resin such as polyethylene, or a ceramic and steel.

[0172] In one embodiment, with the aim to reduce the density and the quantity of matrix (denser than water), Hollow Macrospheres are added.

[0173] Technology Macrospheres technologies are used: See FIGS. 8 and 9.

[0174] Thermoplastic Macropsheres: Hemispheres may be injected and 2 hemispheres may be welded by hot plate process.

[0175] 3. Curable Liquid Resin

[0176] The curable liquid resin monomer or prepolymer is an Epoxy Matrix.

[0177] The resin may be for example a Epoxy Bisphenol A diglycidyl ether based.

[0178] The polymerization initiator may be a amine hardener.

[0179] At ambient temperature, Epoxy Resin may be transparent and has a viscosity similar to hot honey. The Epoxy Resin has a viscosity at 15° C. of from 5200 to 9200 mPa.Math.s. It may have a viscosity at 40° C. of from 300 to 550 mPa.Math.s. Its density may be, at 20° C., of from 1 to 1.5. The hardening of the Epoxy Resin may occur to room temperature, and the post-curring from 40-80° C.

[0180] The polymerization initiator is transparent yellow, with a viscosity similar to water. Its viscosity may be comprised, at 15° C., from 25 to 45 mPa.Math.s. At 40° C., the hardener may have a viscosity of from 8 to 15 mPa.Math.s. Its density may be, at 20° C., of from 0.90 to 1.10.

[0181] The mixing ratio per weight Epoxy Resin/Hardener is comprised of from 50/50 to 100/60.

[0182] The mixture of Hardener and Epoxy Resin may have a viscosity, at 20° C., of from 300 to 530 mPa.Math.s, for example of from 355 to 505, for example about 420 mPa.Math.s. At 50° C., the viscosity may be of from 30 to 70 mPa.Math.s.

[0183] The exothermic peak of the mixture may reach, for example, for a temperature of the mixture regulated to a maximum of 40° C., 140° C. For a temperature of the mixture regulated to a maximum of 30° C., the exothermic peak may reach 55° C. And for a temperature regulated to a maximum of 20° C., there is no exothermic peak.

Example 3: Syntactic Foam Testing

[0184] The main 3 factors to control in order to produce a Foam compliant with requirement are: [0185] The foam Density [0186] The Volume casted [0187] The foam hydrostatic performance (short and long term)

[0188] For the composite syntactic foam, full characterization testing reports are provided to certify the performance of the material versus the application.

[0189] For each Composite Syntactic Foam recipes of the invention, following test are performed:

[0190] 1. Density Control

[0191] The aim of this test is to control that the syntactic foam produced is in accordance with specifications.

[0192] If the density controlled is not in accordance with specifications, the final buoyancy of the product will be wrong and the syntactic foam will not have right performance.

[0193] The density of each component is controlled then the density of syntactic foam manufactured is controlled.

[0194] Density may be controlled using any test available to one of ordinary skill in the art.

[0195] 2. Epoxy Glass Transition Temperature

[0196] The aim of this test is to control that the matrix will have right reticulation level. Glass transition temperature shall be in accordance with syntactic foam specification. If the Glass transition is not in accordance with specification the matrix will not have chemical and mechanical performance and the final product will underperform.

[0197] Reticulation level of the matrix may be controlled using any test available to one of ordinary skill in the art.

[0198] 3. Hydrostatic Strength and Water Absorption Test Instrumented Buoyancy Loss Test.

[0199] Before, during and/or after production, samples of the syntactic foam of the invention are casted in order to control full system performance.

[0200] The aim of this test is to immerse a representative sample and rise up the pressure up to service pressure rated for the recipe. The size sample is: 300 mm diameter and 800 mm length.

[0201] The buoyancy of the sample is registered during the full test.

[0202] After the test is calculated the Buoyancy loss over the service life of the product.

[0203] The duration of the test is as per specification; common values are 96 hours test first part validation test and 24 h test spread on the production.

[0204] Any test procedure available to one of ordinary skill in the art may be used in order to measure the hydrostatic performance of the buoyancy. It may be for example a test as described in the documents

[0205] 4. Effective Buoyancy

[0206] A buoyancy test is carried out in order to control that the buoyancy module uplift complies with requirement.

[0207] In this case the full-scale buoyancy module is immerged in water in order to verify if the buoyancy measured are in accordance with the buoyancy required.

[0208] Any test procedure available to one of ordinary skill in the art may be used in order to control that the buoyancy module uplift complies with requirement. The general principle is described in FIG. 10.

Example 4: Syntactic Foam Performance

[0209] Throughout their design life, the buoyancy modules may be submerged at the design water depth stated in project requirements. These conditions require a syntactic foam suitable for operations at the depth specified.

[0210] During this time, the syntactic foam may have a limited and controlled buoyancy loss due to initial hydrostatic compression, water absorption and hydrostatic creep.

[0211] Therefore, there may be three steps for the determination of buoyancy to meet with requirements: [0212] Buoyancy targeted after manufacturing [0213] The net buoyancy at the maximum operating depth [0214] The net buoyancy at end of service life,

See FIG. 11.

[0215] The aim of the buoyancy analysis is to ensure that the net buoyancy required is always maintained during the design period between the Buoyancy at service pressure and Buoyancy at the end of the service life

[0216] The buoyancy under hydrostatic pressure, is a short term buoyancy. In this case the buoyancy variation (gain or loss) is reversible. If the pressure is removed the value back to the buoyancy targeted after manufacturing. It is thus defined knowing: [0217] The buoyancy targeted after manufacturing, (gain or loss) [0218] The Linear Elastic Hydrostatic Compression due to the sea water pressure (gain or loss)

[0219] The minimum long term buoyancy is the buoyancy under hydrostatic pressure after the design period. It is thus defined knowing: [0220] The buoyancy targeted after manufacturing, taking into account the minimum [0221] The Linear Elastic Hydrostatic Compression due to the sea water pressure, taking into account the minimum [0222] The Buoyancy at the end of the service life due to the non linear permanent buoyancy loss, taking into account the minimum.

[0223] This is illustrated on the FIG. 12.

[0224] The contribution of all the buoyancy loss factors may be taken into account on:

Buoyancy at the end of the service life=Buoyancy after manufacturing+Linear Hydrostatic Buoyancy variation+Non linear permanent buoyancy loss

[0225] Density Recipes Calculation

[00002] $.Math. Buoyancy = V_{Shell} \times (ρ_{fluid} - ρ_{SYNTACTIC .Math. .Math. FOAM})$ $ρ_{SYNTACTIC .Math. .Math. FOAM} = %_{Volume .Math. .Math. Macrosphere} \times ρ_{Macrosphere} + γ_{Process} \times (%_{Volume .Math. .Math. μ .Math. .Math. sphere} \times ρ_{μ .Math. .Math. sphere} + %_{Volume .Math. .Math. Epoxy} \times ρ_{Epoxy})$

[0226] γ.sub.Process factor taking into account, process loss, remaining void in the matrix, shrinkage during polymerization, microsphere breakage ratio. This factor is different for each matrix and microspheres used.

ρ.sub.Epoxy=ρ.sub.Hardener×%.sub.Volume Hardener+ρ.sub.Resin×ρ.sub.Volume Resin

[0227] %.sub.Volume Macrosphere Calulation:

[0228] The amount of spheres in a shell is related to the wall effect of the shell receiving spheres.

[0229] Smaller is the sphere regarding the total volume of the shell more the packing will be optimized.

[0230] The goal is to saturate the inside volume of the shell by macrosphere, taking care the packing, the volume of macrosphere may be inferior to 100%, for example from 50 to 70%.

[0231] In the FIG. 13 is showed the effect of the wall on packing, the porosity is the space between sphere:

%.sub.Volume Macrosphere=1%.sub.porosity

[0232] As demonstrated in the FIG. 13, at 0.5× the diameter of the sphere the average porosity become stable to reach %.sub.porosity close packed=36%.

[0233] From the wall of the shell to 0.5 the diameter of the sphere the average porosity is %.sub.porosity affected by the wall=56%.

[0234] Then the formula to determinate the average packing in the shell is:

%.sub.Volume Msphere=V.sub.wall affected×(1−%.sub.porosity affected by the wall)+V.sub.closed packed×(1−%.sub.porosity close packed)

[0235] V.sub.wall affected is the volume occupied by all halves marcospheres in contact with the shell. This measure may be determined using CAD software (available at CMS IntelliCAD). For simple shape volume V.sub.wall affected can be calculated analytically.

[0236] V.sub.wall affected in m.sup.3

V.sub.closed packed=V.sub.shell−V.sub.wall affected

[0237] V.sub.closed packed in m.sup.3

[0238] See FIG. 14.

Example 5: Example of Manufacturing Process

[0239] This chapter aim to describe the Manufacturing process in order to produce composite syntactic foam of the invention.

[0240] 1. Handling of Raw Material

[0241] In addition to ensuring good standards of industrial hygiene, as well as applying the measures given in the material safety data sheets (MSDS), it is recommended to follow the procedures indicated below in order to avoid contamination of the formulations.

[0242] The resins (components A and B) are available in 2001 steel drums or 1 cubic meter intermediate bulk containers (IBC).

[0243] Each Component is sensitive to water and to oxygen, resulting in a change of material proprieties after polymerization. Containers may be open just before use and the cap with water absorber system may replace the original cap.

[0244] Intermediary tank and feed lines destined to be filled with resin may be clean.

[0245] Container may be placed on retention tank.

[0246] Microspheres may be available in 1 or 2 cubic meter big-bag. Moisture stick microspheres together in order to avoid this effect big-bag may stay closed until installation and use.

[0247] Macrospheres are available in 1 cubic meter big-bag. Big-bag shall be carefully handled spheres shall not receive strokes or impact and thus weakening balls. Big-bag shall stay closed in order to avoid dust on spheres.

[0248] 2. Material Storage

[0249] For Epoxy 2 Components:

[0250] The recommended storage range is from 5° C. to 50° C.

[0251] Under these storage conditions, 24 months shelf life of the product is guaranteed from the date of delivery in the original sealed packing.

[0252] For Microspheres:

[0253] To help ensure ease of storage and handling while maintaining free flowing properties, Glass Bubbles have been made from a chemically stable glass and are packaged in a heavy duty polyethylene bag within a cardboard container.

[0254] Minimum storage conditions should be unopened bags in an unheated warehouse.

[0255] Under high humidity conditions with the ambient temperature cycling over a wide range, moisture can be drawn into the bag as the temperature drops and the air contracts. The result may be moisture condensation within the bag. Extended exposure to these conditions may result in “caking” of the glass bubbles to various degrees. To minimize the potential for “caking” and prolong the storage life, the following suggestions are made: [0256] Carefully re-tie open bags after use. [0257] If the polyethylene bag is punctured during shipping or handling, use this bag as soon as possible, patch the hole, or insert the contents into an undamaged bag.

[0258] During hot and humid months, store in the driest, coolest space available.

[0259] If controlled storage conditions are unavailable, carry a minimum inventory, and process on a first in/first out basis.

[0260] For Macrospheres:

[0261] Macrospheres shall be stored in a dry and free dust area.

[0262] Storage temperature shall not be higher than 70° C.

Example 6: Syntactic Foam Casting Machine Principle

[0263] To process the syntactic foam material, a casting machine is used, for high quality manufacturing and productivity.

[0264] An automatic in line component regulation is used in order to ensure the right mix proportion and the stability of the mix during the casting.

[0265] All parameters are controlled and monitored by the machine and allow to know exactly the properties of the material which is casted: [0266] The casting machine regulates temperature and mass flow rate of each matrix components of matrix. [0267] The special in line degassing remove air bubble from the mix See FIG. 15.

[0268] Before casting: [0269] Intermediate tank are automatically pumped from polymerization initiator and Resin IBC Components are tempered (heated or cooled) in order to reach 24° C. [0270] Metering hopper (F1 and F2) are automatically filled by Fumed silica and micro spheres
During the casting: [0271] Epoxy and polymerization initiator are pumped from the intermediates tanks to the pre-mix binder, the mass flow of each component are regulated using Mass flow meters. [0272] The polymerization initiator and the Resin are mixed in the Pre-Mix binder [0273] At the same time Fillers are distributed at constantan flow with metering hopper and are transferred in the Fillers Hooper. [0274] Then liquids and Fillers are mixed together with an endless screw (This mixing technique not break microspheres) [0275] The vacuum unit remove bubbles from the mix [0276] Finally the Syntactic foam go out mixing head through the output and can be poured in the mould filled with Macrospheres.
After the casting: [0277] The mixing head shall be clean with the automatic cleaning process.

Example 7: Manufacturing Process

[0278] The purpose of the section is to explain the manufacturing process in order to produce Composite Syntactic Foam of the invention.

[0279] The process consists in mixing each component: [0280] Compiling with stoichiometry [0281] Following temperature and duration for each step [0282] Without altering the mechanical characteristics of hollow spheres [0283] Without including air in the mix

[0284] Composite syntactic foam Manufacturing Steps are described in FIG. 16.

[0285] 1. Step of Mixing the Curable Liquid Resin Monomer or Prepolymer with the Polymerization Initiator

[0286] The beginning of the mixing may be realized at the minimum temperature necessary for initializing the polymerization while controlling and limiting exothermic peak during one or more of step(s) a) to e). This minimum temperature may be comprised from 15° C. to 90° C., depending on the nature of the curable liquid resin and of the polymerization initiator.

[0287] During the mixing of the curable liquid resin monomer or prepolymer and the polymerization initiator, the temperature should not exceed 90-120° C., and should be handled under 90-120° C. During Polymerization, epoxies have exothermic reaction, if not controlled this temperature can increase up to burn the core and the shell of the part casted.

[0288] In this embodiment, the temperature shall not rise above about 150° C.

[0289] These temperatures depend on the nature of the curable liquid resin and polymerization initiator, and may be easily determined by general knowledge of one of ordinary skill in the art.

[0290] 2. Step of Mixing the Operable Curable Liquid Resin with the Micro-Elements

[0291] The temperature of mixing the operable curable resin and the micro-element may be regulated, if necessary, to control and limit the exothermic peak. The temperature may be maintained between 15 and 60° C., for example of from 17° C. to 45° C., for example 20 to 40° C., depending on the nature of the resin/polymerization initiator.

[0292] 3. Step of Homogenizing and Degasing the Mixture of Operable Curable Liquid Resin and Micro-Elements

[0293] The temperature of homogenization and degassing may be regulated, if necessary, to control and limit the exothermic peak. The temperature may be maintained between 15 and 50° C., for example of from 17° C. to 45° C., for example 20 to 40° C., depending on the nature of the resin/polymerization initiator.

[0294] 4. Step of Casting the Intermediate Syntactic Foam in the Container

[0295] The temperature of casting the intermediate syntactic foam in the container may be regulated, if necessary, to control and limit the exothermic peak. The temperature may be maintained between 15 and 50° C., for example of from 17° C. to 45° C., for example 20 to 40° C., depending on the nature of the resin/polymerization initiator.

[0296] 5. Step of Hardening the Operable Curable Liquid Resin

[0297] The hardening of the operable curable liquid resin may be achieved by heating the resin, at a temperature comprised from 15 and 50° C., for example of from 17° C. to 45° C., for example 20 to 40° C. In one embodiment, the temperature is handled in order to control and limit the exothermic peak.

Example 8: Calculation Examples of Buoyancy

[0298] 1. Cuboid Shape

[0299] This example will take into account a cuboid shape buoyancy with edges of 1 m (a, height), 2 m (b, width) and 1.5 m (c, depth).

[0300] Recipe Choice

[0301] Parameters are:

TABLE-US-00001 Volumic ratio of Volumic ratio of Volumic ratio of resin hardener μspheres ratio.sub.resin = 26.6% ratio.sub.hardener = 18.4% ratio.sub.μsph = 55% Resin density Hardener density μspheres density ρ.sub.resin = 1140 kg/m.sup.3 ρ.sub.hardener = 970 kg/m.sup.3 ρ.sub.μsph = 200 kg/m.sup.3

[0302] Process factor γ.sub.process=1.05

[0303] Macrospheres diameter D.sub.Msph=25.4 mm

[0304] Macrospheres density ρ.sub.Msph=363 kg/m.sup.3

[0305] Shell Volume and Calculation of the Volume Affected by the Wall:

[00003] $.Math. V_{shell} = a \times b \times c = 1 \times 2 \times 1, 5 = 3 .Math. .Math. m^{3}$ $V_{closed .Math. .Math. packed} = ((a - 2 \times \frac{D_{Msph}}{2}) \times (b - 2 \times \frac{D_{Msph}}{2}) \times (c - 2 \times \frac{D_{Msph}}{2})) = 2.84 .Math. .Math. m^{3}$ $.Math. V_{wall .Math. .Math. affected} = V_{shell} - V_{closed .Math. .Math. packed} = 0.162 .Math. .Math. m^{3}$

[0306] % Macrosphere Calculation:

[00004] $ratioMsph = \frac{V_{wall .Math. .Math. affected}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. wall .Math. .Math. affected}) + \frac{V_{closed .Math. .Math. packed}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. close .Math. .Math. packed}) = 62.9 .Math. %$

[0307] Density Calculation:

[00005] $ρ_{syntactic .Math. .Math. foam} = γ_{Process} \times (%_{Volume .Math. .Math. hardener} \times ρ_{hardener} + %_{Volume .Math. .Math. μ .Math. .Math. sph} \times ρ_{μ .Math. .Math. sph} + %_{Volume .Math. .Math. resin} \times ρ_{resin}) .Math. = 620 .Math. .Math. kg .Math. / .Math. m^{3}$ $ρ_{COMPOSITE .Math. .Math. SYNTACTIC .Math. .Math. FOAM} = {ratio}_{Msph} \times ρ_{Msph} + (1 - {ratio}_{Msph}) \times ρ_{syntactic .Math. .Math. foam} = 458 .Math. .Math. kg .Math. / .Math. m^{3}$

[0308] 2. Cylindrical Shape

[0309] This example takes into account a cylindrical shape buoyancy with a diameter (a) of 2 m and a height (b) of 3 m, for a design depth of 500 m.

[0310] Recipe Choice

[0311] Parameters are:

TABLE-US-00002 Volumic ratio of Volumic ratio of Volumic ratio of resin hardener μspheres ratio.sub.resin = 26.6% ratio.sub.hardener = 18.4% ratio.sub.μsph = 55% Resin density Hardener density μspheres density ρ.sub.resin = 1140 kg/m.sup.3 ρ.sub.hardener = 970 kg/m.sup.3 ρ.sub.μsph = 125 kg/m.sup.3

[0312] Process factor γ.sub.process=1.12

[0313] Macrospheres diameter D.sub.Msph=35.6 mm

[0314] Macrospheres density ρ.sub.Msph=205 kg/m.sup.3

[0315] Shell Volume and Calculation of the Volume Affected by the Wall:

[00006] $V_{shell} = b \times (π \times \frac{a^{2}}{4}) = 9.425 .Math. .Math. m^{3}$ $V_{closed .Math. .Math. packed} = (b - 2 \times \frac{D_{Msph}}{2}) \times π \times \frac{{(a - \frac{D_{Msph}}{2})}^{2}}{4} = 9.15 .Math. .Math. m^{3}$ $V_{wall .Math. .Math. affected} = V_{shell} - V_{closed .Math. .Math. packed} = 0.277 .Math. .Math. m^{3}$

[0316] % Macrosphere Calculation:

[00007] $%_{Volume .Math. .Math. Msph} = \frac{V_{wall .Math. .Math. affected}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. wall .Math. .Math. affected}) + \frac{V_{closed .Math. .Math. packed}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. closed .Math. .Math. packed}) = 63.4 .Math. %$

[0317] Density Calculation:

[00008] $ρ_{syntactic .Math. .Math. foam} = γ_{Process} \times (%_{Volume .Math. .Math. hardener} \times ρ_{Hardener} + %_{Volume .Math. .Math. μ .Math. .Math. sph} \times ρ_{μ .Math. .Math. sph} + %_{Volume .Math. .Math. resin} \times ρ_{resin}) = 615 .Math. .Math. kg .Math. / .Math. m^{3}$ $ρ_{COMPOSITE .Math. .Math. SYNTACTIC .Math. .Math. FOAM} = %_{Volume .Math. .Math. Msph} \times ρ_{Msph} + (1 - %_{Volume .Math. .Math. Msph}) \times ρ_{syntactic .Math. .Math. foam} = 355 .Math. .Math. Kg .Math. .Math. kg .Math. / .Math. m^{3}$

[0318] 3. Buoyancy Module Shape

[0319] This kind of shape is the same kind of shape than distributed buoyancy modules (cf. FIG. 14 B), with:

[0320] a=0.4 m

[0321] b=0.1 m

[0322] c=0.5

[0323] Parameters are:

TABLE-US-00003 Volumic ratio of Volumic ratio of Volumic ratio of resin hardener μspheres %.sub.Volume resin = 26.6% %.sub.Volume hardener = 18.4% %.sub.Volume μsph = 55% Resin density Hardener density μspheres density ρ.sub.resin = 1140 kg/m.sup.3 ρ.sub.hardener = 970 kg/m.sup.3 ρ.sub.μsph = 200 kg/m.sup.3

[0324] Process factor γ.sub.process=1.048

[0325] Macrospheres diameter D.sub.Msph=25.4 mm

[0326] Macrospheres density ρ.sub.Msph=363 kg/m.sup.3

[0327] Shell Volume and Calculation of the Volume Affected by the Wall:

[00009] $.Math. V_{shell} = \frac{c}{2} \times \frac{(a^{2} - b^{2}) \times π}{4} = 0.029 .Math. .Math. m^{3}$ $V_{closed .Math. .Math. packed} = \frac{({(a - \frac{D_{Msph}}{2})}^{2} - {(b - \frac{D_{Msph}}{2})}^{2}) \times \frac{π}{4} \times (c - 2 \times \frac{D_{Msph}}{2})}{2} - ((a - b - D_{Msph}) \times (c - D_{Msph}) \times D_{Msph}) = 0.023 .Math. .Math. m^{3} .Math. .Math. V_{wall .Math. .Math. affected} = V_{shell} - V_{closed .Math. .Math. packed} = 0.006 .Math. .Math. m^{3}$

[0328] % Macrosphere Calculation:

[00010] $%_{Volume .Math. .Math. Msph} = \frac{V_{wall .Math. .Math. affected}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. wall .Math. .Math. affected}) + \frac{V_{closed .Math. .Math. packed}}{V_{shell}} \times (1 - %_{porosity .Math. .Math. close .Math. .Math. packed}) = 59.8 .Math. %$

[0329] Density Calculation:

[00011] $ρ_{syntactic .Math. .Math. foam} = γ_{Process} \times (%_{Volume .Math. .Math. hardener} \times ρ_{hardener} + %_{Volume .Math. .Math. μ .Math. .Math. sph} \times ρ_{μ .Math. .Math. sph} + %_{Volume .Math. .Math. resin} \times ρ_{resin}) = 620 .Math. .Math. kg .Math. / .Math. m^{3}$ $ρ_{COMPOSITE .Math. .Math. SYNTACTIC .Math. .Math. FOAM} = %_{Volume .Math. .Math. Msph} \times ρ_{Msph} + (1 - %_{Volume .Math. .Math. Msph}) \times ρ_{syntactic .Math. .Math. foam} = 466 .Math. .Math. kg .Math. / .Math. m^{3} .Math. .Math. kg .Math. / .Math. m^{3}$

LIST OF REFERENCES

[0330] 1. U.S. Pat. No. 3,622,437. [0331] 2. Ben Aïm and Le Goff, “Effet de paroi dans les empilements désordonnés de sphères et application à la parasité de mélanges binaires”, Powder Technol, 1 (1967/68) 281-290.

SYNTACTIC FOAM, PROCESS OF ITS PREPARATION AND BUOYANCY MATERIAL INCLUDING THE SAME

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Abstract

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Description